As is well known, the World Wide Web (WWW) or the web is a graphical sub-network of the Internet. Through the WWW, a user at a client terminal can obtain information objects, e.g., hypertext markup language (HTML) documents, from different servers connected to the WWW. Each object is identified by a uniform resource locator (URL), and provided by a server associated with the URL to the client terminal through a connection, in accordance with a hypertext transfer protocol (HTTP). Using a conventional browser, the client terminal opens the information objects obtained thereby to allow the user to view the objects.
In accordance with the HTTP version 1.0 which is the current standard, each HTTP connection is typically established to transfer only one information object from a server to a client terminal, and then terminated. That is, even if multiple information objects need to be transferred from the same server to the same client terminal, the process of establishing and terminating an HTTP connection is repeated for each object transfer. However, use of such a connection to obtain objects may cause an "information inconsistency" problem. This problem, described below, arises when related information is distributed among a group of information objects in a server.
For example, a book may be presented by a server in chapters. Individual objects in the server representing different chapters of the book are logically connected, and form what is referred to as a "logical group." Individual objects representing quotes of the stocks of different companies at a particular time may form another logical group as a stock analyst may utilize the stock quotes to perform a market analysis corresponding to that particular time. However, objects in a logical group, e.g., those representing stock quotes, may be updated frequently. As a result, it is likely that after a client terminal receives a first object in a logical group through an HTTP connection, one or more of the remaining objects in the group are updated. When the client terminal receives a second object from the group through another HTTP connection, the second object may have been updated and is not contemporaneous with the first object. In that case, the client terminal receives timeinconsistent information as the first and second objects do not come from the same time-version of the logical group. In the stock quote example, such an information inconsistency problem frustrates the aforementioned market analysis which must be based on contemporaneous stock quotes or information objects belonging to the same version.
An attempt has been made to rectify the information inconsistency problem. This attempt calls for making the server unavailable for some time while an information update is being performed. This ensures that information objects in a logical group obtained in each session while the server is available come from the same version of the logical group. However, such an attempt incurs disruption in the service by the server during each update, which is undesirable and annoying especially when the service involves provision of real-time information, e.g., the aforementioned stock quotes, flight arrival and departure information, etc., which needs to be updated frequently.
Accordingly, there exists a need for a methodology whereby a server can effectively provide in a consistent manner information which is frequently updated, without having its service disrupted.